A Scotland Yard spokesman said yesterday: “PC Carol Howard is bringing an employment tribunal claim against the Metropolitan Police Service citing racial and sexual discrimination.

“The Service will robustly defend the claim.”

DPG officer Keith Wallis was jailed for 12 months last month for lying about witnessing the so called Plebgate scandal involving a confrontation between Chief Whip Andrew Mitchell and DPG officers at the gates of Downing Street in September 2012.

Also last month, it was revealed three DPG officers had been arrested over claims they exchanged “extreme” pornography on their mobile phones.